 /*******************************************************************************
  * Copyright (c) 2005, 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.ui.contexts;

 import java.util.Collection ;

 import org.eclipse.core.commands.contexts.Context;
 import org.eclipse.core.commands.contexts.IContextManagerListener;
 import org.eclipse.core.expressions.Expression;
 import org.eclipse.swt.widgets.Shell;
 import org.eclipse.ui.services.IServiceWithSources;

 /**
  * <p>
  * Provides services related to contexts in the Eclipse workbench. This provides
  * access to contexts.
  * </p>
  * <p>
  * This interface should not be implemented or extended by clients.
  * </p>
  *
  * @since 3.1
  */
 public interface IContextService extends IServiceWithSources {

     /**
      * The identifier for the context that is active when a shell registered as
      * a dialog.
      */
     public static final String CONTEXT_ID_DIALOG = "org.eclipse.ui.contexts.dialog"; //$NON-NLS-1$

     /**
      * The identifier for the context that is active when a shell is registered
      * as either a window or a dialog.
      */
     public static final String CONTEXT_ID_DIALOG_AND_WINDOW = "org.eclipse.ui.contexts.dialogAndWindow"; //$NON-NLS-1$

     /**
      * The identifier for the context that is active when a shell is registered
      * as a window.
      */
     public static final String CONTEXT_ID_WINDOW = "org.eclipse.ui.contexts.window"; //$NON-NLS-1$

     /**
      * The type used for registration indicating that the shell should be
      * treated as a dialog. When the given shell is active, the "In Dialogs"
      * context should also be active.
      */
     public static final int TYPE_DIALOG = 0;

     /**
      * The type used for registration indicating that the shell should not
      * receive any key bindings be default. When the given shell is active, we
      * should not provide any <code>EnabledSubmission</code> instances for the
      * "In Dialogs" or "In Windows" contexts.
      *
      */
     public static final int TYPE_NONE = 1;

     /**
      * The type used for registration indicating that the shell should be
      * treated as a window. When the given shell is active, the "In Windows"
      * context should also be active.
      */
     public static final int TYPE_WINDOW = 2;

     /**
      * <p>
      * Activates the given context within the context of this service. If this
      * service was retrieved from the workbench, then this context will be
      * active globally. If the service was retrieved from a nested component,
      * then the context will only be active within that component.
      * </p>
      * <p>
      * Also, it is guaranteed that the contexts submitted through a particular
      * service will be cleaned up when that services is destroyed. So, for
      * example, a service retrieved from a <code>IWorkbenchPartSite</code>
      * would deactivate all of its contexts when the site is destroyed.
      * </p>
      *
      * @param contextId
      * The identifier for the context which should be activated; must
      * not be <code>null</code>.
      * @return A token which can be used to later cancel the activation. Only
      * someone with access to this token can cancel the activation. The
      * activation will automatically be cancelled if the context from
      * which this service was retrieved is destroyed.
      */
     public IContextActivation activateContext(String contextId);

     /**
      * <p>
      * Activates the given context within the context of this service. The
      * context becomes active when <code>expression</code> evaluates to
      * <code>true</code>. This is the same as calling
      * {@link #activateContext(String, Expression, boolean)} with global==<code>false</code>.
      * </p>
      * <p>
      * Also, it is guaranteed that the context submitted through a particular
      * service will be cleaned up when that services is destroyed. So, for
      * example, a service retrieved from a <code>IWorkbenchPartSite</code>
      * would deactivate all of its handlers when the site is destroyed.
      * </p>
      *
      * @param contextId
      * The identifier for the context which should be activated; must
      * not be <code>null</code>.
      * @param expression
      * This expression must evaluate to <code>true</code> before
      * this context will really become active. The expression may be
      * <code>null</code> if the context should always be active.
      * @return A token which can be used to later cancel the activation. Only
      * someone with access to this token can cancel the activation. The
      * activation will automatically be cancelled if the context from
      * which this service was retrieved is destroyed.
      *
      * @see org.eclipse.ui.ISources
      * @since 3.2
      */
     public IContextActivation activateContext(String contextId,
             Expression expression);

     /**
      * <p>
      * Activates the given context within the context of this service. The
      * context becomes active when <code>expression</code> evaluates to
      * <code>true</code>. If global==<code>false</code> then this service
      * must also be the active service to activate the context.
      * </p>
      * <p>
      * Also, it is guaranteed that the context submitted through a particular
      * service will be cleaned up when that services is destroyed. So, for
      * example, a service retrieved from a <code>IWorkbenchPartSite</code>
      * would deactivate all of its handlers when the site is destroyed.
      * </p>
      *
      * @param contextId
      * The identifier for the context which should be activated; must
      * not be <code>null</code>.
      * @param expression
      * This expression must evaluate to <code>true</code> before
      * this context will really become active. The expression may be
      * <code>null</code> if the context should always be active.
      * @param global
      * Indicates that the handler should be activated irrespectively
      * of whether the corresponding workbench component (e.g.,
      * window, part, etc.) is active.
      * @return A token which can be used to later cancel the activation. Only
      * someone with access to this token can cancel the activation. The
      * activation will automatically be cancelled if the context from
      * which this service was retrieved is destroyed.
      *
      * @see org.eclipse.ui.ISources
      * @since 3.2
      */
     public IContextActivation activateContext(String contextId,
             Expression expression, boolean global);

     /**
      * <p>
      * Activates the given context within the context of this service. The
      * context becomes active when <code>expression</code> evaluates to
      * <code>true</code>.
      * </p>
      * <p>
      * Also, it is guaranteed that the context submitted through a particular
      * service will be cleaned up when that services is destroyed. So, for
      * example, a service retrieved from a <code>IWorkbenchPartSite</code>
      * would deactivate all of its handlers when the site is destroyed.
      * </p>
      *
      * @param contextId
      * The identifier for the context which should be activated; must
      * not be <code>null</code>.
      * @param expression
      * This expression must evaluate to <code>true</code> before
      * this context will really become active. The expression may be
      * <code>null</code> if the context should always be active.
      * @param sourcePriorities
      * The source priorities for the expression.
      * @return A token which can be used to later cancel the activation. Only
      * someone with access to this token can cancel the activation. The
      * activation will automatically be cancelled if the context from
      * which this service was retrieved is destroyed.
      *
      * @see org.eclipse.ui.ISources
      * @deprecated Use
      * {@link IContextService#activateContext(String, Expression)}
      * instead.
      */
     public IContextActivation activateContext(String contextId,
             Expression expression, int sourcePriorities);

     /**
      * Adds a listener to this context service. The listener will be notified
      * when the set of defined contexts changes. This can be used to track the
      * global appearance and disappearance of contexts.
      *
      * @param listener
      * The listener to attach; must not be <code>null</code>.
      * @since 3.2
      */
     public void addContextManagerListener(IContextManagerListener listener);

     /**
      * Deactivates the given context within the context of this service. If the
      * handler was context with a different service, then it must be deactivated
      * from that service instead. It is only possible to retract a context
      * activation with this method. That is, you must have the same
      * <code>IContextActivation</code> used to activate the context.
      *
      * @param activation
      * The token that was returned from a call to
      * <code>activateContext</code>; must not be <code>null</code>.
      */
     public void deactivateContext(IContextActivation activation);

     /**
      * Deactivates the given contexts within the context of this service. If the
      * contexts were activated with a different service, then they must be
      * deactivated from that service instead. It is only possible to retract
      * context activations with this method. That is, you must have the same
      * <code>IContextActivation</code> instances used to activate the
      * contexts.
      *
      * @param activations
      * The tokens that were returned from a call to
      * <code>activateContext</code>. This collection must only
      * contain instances of <code>IContextActivation</code>. The
      * collection must not be <code>null</code>.
      */
     public void deactivateContexts(Collection activations);

     /**
      * Returns the set of active context identifiers.
      *
      * @return The set of active context identifiers; this value may be
      * <code>null</code> if no active contexts have been set yet. If
      * the set is not <code>null</code>, then it contains only
      * instances of <code>String</code>.
      * @since 3.2
      */
     public Collection getActiveContextIds();

     /**
      * Retrieves the context with the given identifier. If no such context
      * exists, then an undefined context with the given id is created.
      *
      * @param contextId
      * The identifier to find; must not be <code>null</code>.
      * @return A context with the given identifier, either defined or undefined.
      */
     public Context getContext(String contextId);

     /**
      * Returns the collection of all of the defined contexts in the workbench.
      *
      * @return The collection of contexts (<code>Context</code>) that are
      * defined; never <code>null</code>, but may be empty.
      * @since 3.2
      */
     public Context[] getDefinedContexts();

     /**
      * Returns the collection of the identifiers for all of the defined contexts
      * in the workbench.
      *
      * @return The collection of context identifiers (<code>String</code>)
      * that are defined; never <code>null</code>, but may be empty.
      */
     public Collection getDefinedContextIds();

     /**
      * Returns the shell type for the given shell.
      *
      * @param shell
      * The shell for which the type should be determined. If this
      * value is <code>null</code>, then
      * <code>IContextService.TYPE_NONE</code> is returned.
      * @return <code>IContextService.TYPE_WINDOW</code>,
      * <code>IContextService.TYPE_DIALOG</code>, or
      * <code>IContextService.TYPE_NONE</code>.
      */
     public int getShellType(Shell shell);

     /**
      * <p>
      * Reads the context information from the registry and the preferences. This
      * will overwrite any of the existing information in the context service.
      * This method is intended to be called during start-up. When this method
      * completes, this context service will reflect the current state of the
      * registry and preference store.
      * </p>
      */
     public void readRegistry();

     /**
      * <p>
      * Registers a shell to automatically promote or demote some basic types of
      * contexts. The "In Dialogs" and "In Windows" contexts are provided by the
      * system. This a convenience method to ensure that these contexts are
      * promoted when the given is shell is active.
      * </p>
      * <p>
      * If a shell is registered as a window, then the "In Windows" context is
      * enabled when that shell is active. If a shell is registered as a dialog --
      * or is not registered, but has a parent shell -- then the "In Dialogs"
      * context is enabled when that shell is active. If the shell is registered
      * as none -- or is not registered, but has no parent shell -- then the
      * neither of the contexts will be enabled (by us -- someone else can always
      * enabled them).
      * </p>
      * <p>
      * If the provided shell has already been registered, then this method will
      * change the registration.
      * </p>
      *
      * @param shell
      * The shell to register for key bindings; must not be
      * <code>null</code>.
      * @param type
      * The type of shell being registered. This value must be one of
      * the constants given in this interface.
      *
      * @return <code>true</code> if the shell had already been registered
      * (i.e., the registration has changed); <code>false</code>
      * otherwise.
      */
     public boolean registerShell(Shell shell, int type);

     /**
      * Removes a listener from this context service.
      *
      * @param listener
      * The listener to be removed; must not be <code>null</code>.
      * @since 3.2
      */
     public void removeContextManagerListener(IContextManagerListener listener);

     /**
      * <p>
      * Unregisters a shell that was previously registered. After this method
      * completes, the shell will be treated as if it had never been registered
      * at all. If you have registered a shell, you should ensure that this
      * method is called when the shell is disposed. Otherwise, a potential
      * memory leak will exist.
      * </p>
      * <p>
      * If the shell was never registered, or if the shell is <code>null</code>,
      * then this method returns <code>false</code> and does nothing.
      *
      * @param shell
      * The shell to be unregistered; does nothing if this value is
      * <code>null</code>.
      *
      * @return <code>true</code> if the shell had been registered;
      * <code>false</code> otherwise.
      */
     public boolean unregisterShell(Shell shell);
 }

